This application claims the benefit of U.S. Provisional Application Serial No. 60/325,698, entitled Mortise Lock, filed on Sep. 28, 2001 and is a Continuation-In-Part application of U.S. application Ser. No. 10/219,140 filed Aug. 15, 2002, entitled Mortise Latch.
Tubular latches are the most common latching devices used for residential and commercial doors today. They are available in two xe2x80x9cbacksets,xe2x80x9d 2xc2xe inches and 2xe2x85x9c inches. Backset is the distance from the face of the latch to the center of the latch hub/spindle. Tube latches also typically have two spring strengths, one spring strength for levers and one spring strength for knobs. The lever latch has a relatively strong spring for several reasons. First, the spring is strong to support the weight of the levers which are cantilevered from the center of the latch hub. Second, the spring is strong to resist the added torque created by the lever. The knob latch has a relatively weaker spring since the weight of its knobs is evenly distributed around the latch hub. Additionally, the knob is smaller and therefore a user applies less torque to the latch hub when rotating the knob.
Tubular latches also come in an assortment of variations. Typically, manufacturers use one of two finishes for the latch bolt, satin brass and satin nickel. A tubular latch may also be available in either a xe2x80x9cpassagexe2x80x9d type or a xe2x80x9cprivacyxe2x80x9d type. A passage latch is used on doors where no privacy is required such as closets, pantries, laundry rooms, and the like. A privacy latch is used where privacy is required, such as bathrooms, bedrooms, and the like. The privacy feature is integral to the latch body. A pushbutton operates perpendicular to the face of the door to engage the privacy feature and prevent the latch from allowing the door to open. Pushing the pushbutton towards the latch activates the privacy feature and rotating the knob or lever about the latch hub cancels the privacy feature and allows the latch to be unlatched.
Tube latches are required to fit a specific door preparation. The maximum diameter of the latch body is typically one inch. The face plate is typically one inch by two inches. The backset is either 2xe2x85x9c inches or 2xc2xe inches. Privacy latches are typically used on doors predrilled with a 2xe2x85x9 inch hole through the door faces.
In the past, lock dealers were required to inventory specific latches for each combination of backset, spring strength, finish, and privacy or passage type. This resulted in the dealer having to inventory numerous individual latches. The present invention allows one latch to be used for knob strength, lever strength, and backset (2xe2x85x9c inch or 2xc2xe inch). A privacy adapter may be added for the privacy feature. Therefore, a dealer will only have to inventory one latch for each finish, e.g., a satin brass latch and a satin nickel latch, and one privacy adaptor.
A conventional tubular latch as shown in FIG. 1 includes a latch L resiliently held in a housing S fixed in a tubular hole formed in a door R and operatively retracted for opening the door by biasing a door handle H (direction R1) whereby a cam C as rotated (in direction R2) by the handle H will pull a driving plate D secured with the latch L to retract the latch L in rearward direction R3 for opening the door.
For biasing the handle H for opening the door, a rotating angle A (such as 70 degrees) provides a stroke L2 for retracting the latch L in direction R3 for opening the door. This is equal to an arc length of the rotated cam C of the handle H and the retraction of the latch L is directly actuated by rotating the cam C and handle H.
U.S. Pat. No. 5,020,836 discloses a tubular latch that includes a biasing lever pivotally mounted on the housing of the latch. Here, the novel feature of this invention is the addition of a biasing lever and related structure which allows for a smaller degree of handle rotation to fully open the latch bolt. This patent is fully incorporated by reference.
A tubular latch is provided which includes a latch case, a latch bolt, a hub having a cam, a slider member, a latch spring adjuster plate, and a slider member spring. The latch bolt is axially movable within the latch case from an extended position to a retracted position. The hub is rotatably mounted within the latch case and receives a door handle shaft. The hub is rotatable from a first position wherein the latch bolt is in the extended position to a second position wherein the latch bolt is in the retracted position. The cam is integral to an outer surface of the hub and has one or two driving surfaces. Rotational movement of the hub causes the driving surface to rotate with the hub. The slider member is movable from a first axial position in the latch case wherein the slider member is in an extended position to a second axial position in the latch case wherein the slider member is in a retracted position. The slider member is moveable by rotational movement of the hub causing the driving surface of the cam to drive the slider member from the extended position to the retracted position. The latch spring adjuster plate is moveable axially within the latch case and is adjustable and securable to a desired axial position within the latch case. Finally, a slider member spring is included for biasing the slider member away from the latch spring adjuster plate, whereby changing of the desired axial position of the latch spring adjuster plate changes an initial compression amount of the slider member spring.
One or more adjuster plate screws may be used for securing the latch spring adjuster plate to the desired position within the case. The adjuster plate screws may includes a screw head accessible from the outside of the casing. The screw head is preferably adjacent to the latch bolt. A latch bolt shaft connected between the latch bolt and the slider member may be included that is adjustable in length. Here, the latch bolt shaft may include a front latch bolt portion and a rear slider member portion where the front latch bolt portion and the rear slider member portion are adapted to be secured to one another by a spring clip. Finally, the latch bolt shaft may be a one-piece integral unit where the shaft has a plurality of grooves. One of the grooves may be for being received in a slider member keyhole slot to allow for effective adjustability of length of the latch bolt.